Joseph Fazio

Fatalities of Heterogeneous Street Traffic

A unique feature of large South Asian cities is the composition of their urban street traffic. Because many different traffic entities of varying size continuously interact on the street, the traffic mixture is heterogeneous. Heterogeneous traffic increases street capacity. Homogeneous traffic prevails in most North American, European, and Australian cities. Two broad categories comprise heterogeneous traffic: namely, motorized vehicles and nonmotorized entities. After collecting geometric, composition, speed, and conflict data at 14 midblock sites, heterogeneous traffic was examined at a microscopic level. The best model shows that the high-fatality midblock sites correlate to unidirectional street widths at a +0.89 correlation coefficient. The degree of heterogeneity and motorized traffic flow had the strongest relationship with street width at a +0.99 correlation coefficient. Given constant motor vehicle flow, the analyses revealed that when the traffic heterogeneity index approached 1 (i.e., 50 percent motorized and 50 percent nonmotorized), fewer midblock fatalities occurred.